Stability of waste-based zeolite supported CaO catalyst for biodiesel production from waste oily feedstocks

Abstract

Waste-based zeolite supported CaO catalyst (20CaO/ZMFA) was synthesized by ultrasound-assisted impregnation from alcoholic suspension. Zeolite was previously synthesized from lignite coal fly ash (FA) by alkali activation in miniature rotating autoclave reactors (6.25 M NaOH, 260 °C, 4 h), whereas CaO was prepared by chicken eggshell (ES) calcination (900 ºC, 4 h). The final catalyst was obtained by precursor calcination at 550 °C, 4 h. The obtained catalyst was used for catalyst stability tests (reusability and leaching) in transesterification (methanol/oil molar ratio of 12/1, catalyst concentration of 4 wt%, and temperature of 60 °C) of three types of oily feedstocks, fresh sunflower oil (SFO), waste cooking oil (WCO) and model thermal treated (230 °C, 5 days) sunflower oil (SFOTT). The concentration of triacylglycerols (TAGs) and fatty acid methyl esters (FAMEs) was determined by GC and HPLC, respectively. The 20CaO/ZMFA exhibited high activity (FAME content > 96.5 % for 180 min) in the transesterification of all three oily feedstocks. The stability tests are shown that catalyst is stable even in four reaction cycles for SFO and WCO, whereas the Ca 2+ leaching was significantly lower compared to similar catalytic systems.